Refractory brick

ABSTRACT

A REFRACTORY BRICK ADAPTED FOR USE IN FURNACE ROOF CONSTRUCTION AND HAVING SIDE FACES AND END FACES AND A CASING SHEET OF OXIDIZABLE METAL CARRIED ON AT LEAST ONE OF THE SIDE FACES, THE CASING INCLUDING A SHEET CHARACTERIZED BY A PLURALITY OF SPACING PORTIONS PROJECTING FROM ONE SURFACE AND A PLURALITY OF RECESSES DISPOSED IN THE OTHER SURFACE THEREOF IN ALIGNMENT WITH THE SPACING PORTIONS, INDIVIDUAL SPACING PORTIONS AND RECESSES BEING DISCONTINUOUS WITH RESPECT TO A STRAIGHT LINE DISPOSED IN THE PLANE OF THE SHEET. PREFERABLY, THE SPACING PORTIONS ARE DISPOSED IN SURFACE ENGAGEMENT WITH THE BRICK SIDE FACE AND FUNCTION TO SPACE THE ONE SURFACE OF THE SHEET THEREFROM. THE RELATIVE SIZE, CONFIGURATION AND POSITIONING OF THE SPACING PORTIONS AND RECESSES OF THE SHEET PERMITS SUBSTANTIALLY COMPLETE OXIDATION THEREOF DURING USE WITHOUT RESULTING IN GROWTH IN OVERALL SHEET THICKNESS, PREVENTS INTERLOCKING OF LIKE SHEETS CARRIED ON ADJACENT BRICKS DURING INSTALLATION THEREOF IN A FURNACE ROOF, AND MAINTAINS UNIFORM BEARING STRESS CONDITIONS IN FURNACE ROOF BRICK JOINTS.

March 2, 1971 J. STEIN REFRACTORY BRICK 2 Sheets-Sheet 1 Filed Aug. 1, 1968 March 2, 1971 J1. STEIN 3,566,571

REFRACTORY BRICK Filed Aug. l. 1968 v,2 Sheets-Sheet 2 /A/ VEN TO/Z, Jose/2H L. 5TH/v United States Patent Oce Patented Mar. 2, 1971 3,566,571 REFRACTORY BRICK Joseph L. Stein, Cherry Hill, NJ., assignor to General Refractories Company, Philadelphia, Pa. Filed Aug. 1, 1968, Ser. No. 749,468 Int. Cl. F23m 5/02 U.S. Cl. 52-598 2 Claims ABSTRACT F THE DlSCLOSURE A refractory brick adapted for use in furnace roof construction and having side faces and end faces and a casing sheet of oxidizable metal carried on at least one of the side faces, the casing including a sheet characterized by a plurality of spacing portions projecting from one surface and a plurality of recesses disposed in the other surface thereof in alignment with the spacing portions, individual spacing portions and recesses being discontinuous with respect to a straight line disposed in the plane of the sheet. Preferably, the spacing portions are disposed in surface engagement with the brick side face and function to space the one surface of the sheet therefrom. The relative size, configuration and positioning of the spacing portions and recesses of the sheet permits substantially complete oxidation thereof during use without resulting in growth in overall sheet thickness, prevents interlocking of like sheets carried on adjacent bricks during installation thereof in a furnace roof, and maintains uniform bearing stress conditions in furnace roof brick joints.

Recently there has been developed high-fired basic brick having high hot strength which is particularly adapted for use in furnace roof and arch construction. However, while high-fired basic brick has been proven to give better roof service than conventional chemically bonded basic brick, difficulties have been encountered in use due to expansion problems developed because of oxidation of the steel casing conventionally provided on furnace brick. Unlike chemically bonded basic brick, little of the oxidized casing is found to be absorbed by high-fired basic brick and there is less of a tendency for a high-fired basic brick to crush or undergo plastic deformation adjacent the hot surface of the roof and thus relieve the expansion stress set up in the furnace due to casing oxide layer growth.

The magnitude of the problem involving casing oxidation will be apparent when considering that with mild steel casings of the type conventionally employed, the total potential growth due to oxidation results in an approximate doubling of casing thickness. Notwithstanding the fact that presently available casings are normally formed from thin sheet steel of between 18 and 24 gage, the total potential growth of the casings has been found to result in roof failure unless compensation is provided therefor.

Various solutions have been proposed to relieve or minimize expansion stress resulting from oxidation of brick casings. In this respect it has been proposed to include a compressible asbestos sheet in the joints between bricks for the purpose of compensating for both expansion of brick casings due to oxidation and thermal expansion of the bricks. However, the provision of asbestos sheets complicates brick installation, increases construction costs, interferes with desired bonding of casing to brick, and has been found to result in a higher oxidation state of the casing. Also, it has been proposed to reduce the degree of expansion in a furnace roof by decreasing casing thickness and by increasing the dimensions of the bricks. However, these proposals fail to completely solve the oxidation problem or bring overall roof expansion within desired limits.

Also, it has been proposed to compensate for thermal expansion of the individual bricks forming a furnace roof by providing brick casings or spacers with dimples, embossments or corrugations which permit the casing to collapse under high stress conditions. For instance, in Reissue Patent 25,755, there is disclosed a spacer, wherein one of a pair of facing plates is provided adjacent the lower or hot end portion of the brick with a pair of embossments which project from the surface of such plate into engagement with a plate carried on an adjacent brick. While this construction compensates in part for thermal expansion of the bricks, it does not compensate for expansion due to oxidation of the spacer plates themselves. Further, when employing this type of structure, difficulty has been encountered in achieving proper alignment of the embossments across any given transverse element or ring of the roof, thereby resulting in improper alignment of the forces which are set up due to thermal expansion of bricks and oxidation growth of the spacer plates. Misalignment of forces has been found to cause snaking or curvature of the individual bricks along the roof element or ring which may result in complete failure of the roof. Simple spacers 0r pairs of dimples in thin steel sheet casings do not possess adequate strength to resist the load between brick in large sprung arches and have been known to collapse in constructed arches and, therefore, do not satisfactorily provide expansion relief for plate oxidation or thermal expansion during service.

Further, in Austrian Patent 238,621, there is disclosed a brick casing wherein an oxidizable metal sheet is provided with corrugations extending either longitudinally or transversely of a brick so as to form a yieldable joint between adjacent bricks. However, the projecting crests of the corrugations tend to promote interlocking between mating casing surfaces when bricks are forced to slide into place. Interlocking during brick laying not only increases time consumed during installation and thus the cost of the roof, but also tends to produce misalignment of forces across the roof element in the manner mentioned above. Additionally, in this type of structure the bearing stress which individual joints will sustain will vary substantially depending upon the alignment or the relative misalignment of the casing plate crests, and there exists a tendency for the plate corrugations to collapse when forces present in the roof structure during use tend to force an adjacent brick or bricks to move in a direction transversely of the corrugations. When corrugations extend longitudinally, hot furnace gases freely iiow through the joints undesirably heating the refractory coller zones, causing premature oxidation, and burning out of the spacer plates.

Further, it has been proposed to employ casing formed from metals which are less subject to oxidation than conventionally employed low carbon steel. However, use of such metal both increases the cost of construction and may require modification of presently available casing applying equipment.

ln accordance with the present invention there is provided a novel furnace brick casing designs, which permits the utilization of conventional steel casing material with high-fired basic brick, while avoiding the disadvantages of the prior art. The casing is preferably formed by either roller or stamp embossing a flat sheet, usually from a coil, of oxidizable metal, such as conventionally employed cold rolled low carbon steel, to provide a plurality of aligned projections or dimples and recesses on the respective sides of the casing sheet. The extent to 4which the sheet is deformed, i.e. the growth in sheet thickness which corresponds to the height of the projections, depends on the type of metal employed and is preferably at least equal to the growth in thickness of the non-embossed sheet due to oxidation expected to be encountered during use. The projecting portions, which serve to space the non-ernbossed portions of the casing sheet either from the surface of the brick or from a casing carried on an adjoining brick when installed in a roof structure, cooperate with the casing sheet recesses to dene cavities or voids adapted to receive the oxidized layer formed on the casing sheet while permitting gradual deformation of the projections upon oxidation thereof. The thus formed casing, even though completely oxidized during use has been found to undergo little or no increase in overall thickness.

Also, the casing is additionally employed to compensate for thermal expansion of the bricks by increasing the height of the projections over that required to compensate for oxidation growth. In this case the bearing strength of such projection may be accurately controlled to permit collapse thereof during use.

In a preferred embodiment of the present invention the casing is formed from a single metal sheet having a plurality of projections and recesses arranged in a closely spaced uniform pattern. The sheet is adapted to be wound around the side faces of the brick to form a casing structure of generally rectangular cross-section, wherein the projections serve to space the non-embossed portions of the sheet from the brick faces.

Uniformity of pattern permits a successive casing sheet to be severed from an elongated sheet or web of embossed sheet material without regard to the point at which the sheet is to be severed and serves to provide uniform bearing characteristic throughout the joint between adjacent bricks of a roof structure.

By making the casing projections and recesses individually discontinuous with respect to any given straight line lying in a plane defined -by the casing sheet, there is produced a casing design wherein the non-embossed por tions of the outwardly facing surfaces of the casing, which bound the recesses, serve to present a fiat unobstructed bearing surface to a like surface on an adjacent brick, thereby preventing interlocking and decreasing the area of frictional surface contact between adjacent brick casings. Also, by arranging the projections and recesses in the manner described, diverse projection and recess configurations may be employed depending upon the structural and operational requirements of the casing. In this respect, the projections and recesses may be formed with tapered side wall surfaces to permit controlled collapse or deformation of the projections due to the growth of an oxide layer thereon and to make the individual projections more resistant to deformation or collapse should forces present in a roof structure cause adjacent bricks to slide with respect to one another, Also, the projections and recesses may be formed with relatively straight side wall surfaces in order to increase the bearing strength of relatively high gage casing sheet material. Alternately, both tapered and straight wall configurations may be employed in a single casing structure. In the latter case, tapered Wall projections would be positioned on that portion of the casing which covers the lower or hot end of the brick body to be consumed during furnace operation and the straight wall projections would be employed on the remaining portions of the casing to maximize the bearing strength of the casing structure.

Alternative casing embodiments are also anticipated, wherein embossments on two or even three side faces of the 'brick may be omitted, and wherein the projection and recess design and arrangement on the casing sheet permits to space non-embossed portions of the sheet from a casing sheet of either like or fiat surface configuration carried on a joining brick of a roof structure.

The nature of the present invention will be more fully understood by reference to the following description, taken with the accompanying drawings, wherein:

FIG. l is a perspective view of the preferred embodiment of a refractory brick of the present invention having an oxidizable metal casing carried thereon;

FIG. 2 is a fragmentary sectional view taken generally along the line 2-2 in FIG. l;

FIG. 3 is a fragmentary side elevational view of the brick illustrated in FIG. 1;

FIG. 4 is a plan view of the surface of the casing disposed adjacent to one side face of the brick;

FIG. 5 is an end view illustrating one manner in which the casing design illustrated in FIG. l may be modified;

FIG. 6 is a fragmentary view illustrating a joint between adjacent bricks having a further modification of the casing design shown in FIG. 1;

FIG. 7 is a view similar to FIG. 1, but showing a modified casing spacing portion design;

FIG. 8 is a fragmentary sectional view taken generally along the line 8 8 in FIG. 7;

FIG. 9 is a fragmentary side elevational View of the brick illustrated in FIG. 7;

FIG. 10 is a plan View of the surface of the casing disposed adjacent to one side face of the brick illustrated in FIG. 7;

FIG. 11 is a fragmentary view illustrating a joint between adjacent bricks having casings similar to that illustrated in FIG. 7; and

FIG. 12 is a fragmentary view illustrating a still further casing spacing portion design.

A preferred embodiment of the refractory brick according to the present invention s shown in FIG. l as including a molded brick body, generally designated as 1, having first and second pairs of oppositely facing side faces 2a, 2b, and 2c, 2d respectively, and opposed end faces 3a, 3b, and an oxidizable metal casing, generally designated as 4 which is carried on the four side faces of the brick body. Permanent positioning of casing 4 on brick body 1 may be effected by any suitable means, such as recesses 5 which are provided in brick side face 2a and adapted to receive casing keying projections 6 in the [manner shown particularly in FIG. 2. Alternatively, recesses 5 may be disposed in any one of the other brick side faces.

For purposes of reference, it will be understood that refractory bricks of the type disclosed are adapted to be positioned in a furnace roof or each with the first pair of side faces 2a, 2b, disposed in a facing relationship with adjoining bricks of a transverse roof element or ring, as indicated by ring guide arrows 7, and with the second pair of side faces 2c, 2b disposed in facing relationship with brick of vadjoining rings, not shown. The opposed end faces 3a, 3b of brick 1 cooperate with adjoining bricks to define the inwardly and outwardly facing surfaces of the roof, which are termed hot and cold surfaces, respectively. lFurther, it will be understood that end faces 3a, 3b may be of either square or rectangular configuration and that the end face forming the inwardly facing or hot surface of the roof, as for example end face 3b, not shown in FIG. 1, may be of less area than end face 3a forming the outwardly facing or cold surface of the roof to facilitate installation of the brick in a curved surface furnace roof structure. Brick body 1 is preferably formed with a recess i8 which extends lengthwise of either of brick side faces 2c, 2d for the reasons to be hereinafter discussed.

Although the casing of the present invention is described as possessing particular utility when used with brick bodies of the high strength type known as high fired basic brick having a content of at least about 50% magnesium oxide and varying amounts of other oxides including oxides of chromium, silicon, iron and aluminum, it will be clearly understood that it may be employed with improved results in combination with the more conventional chemically bonded basic bricks.

Preferably, casing 4 is formed by a process including the steps of roller or stamp embossing an elongated sheet or web of conventional readily oxidizable metal casing material, such as mild cold rolled steel, and thereafter transversely severing the embossed sheet or web to produce the length of embossed sheet material required to form the casing. In the embodiment shown in FIG. l, the length of sheet material severed is suiiicient to permit the sheet material to be wrapped completely around the brick body side faces, whereafter mating marginal edges of the sheet material, which overlap in the area of body recess 8, are joined, as by spot welding at 9, to form the completed casing structure. Keying projection 6 may 'ne formed during the sheet embossing step or after assembly of the completed casing on the brick body. Preferably one marginal edge portion of the casing sheet is deformed, as at 10, during the severing operation to permit such edge portion to lie within recess 8 and thus avoid a bulge on the side of the casing. The depth of recess 8 is made suilicient to both accommodate the deformed marginal edge portion of the sheet and the increase in double sheet thickness expected to be encountered due to oxidation.

By providing a wrap around casing structure wherein a casing sheet is disposed one on each side face of the brick body, there is created a monolithic roof structure, wherein the individual bricks are physically locked with respect to all adjacent bricks due to bonding of adjacent brick casings under high temperature furnace operating conditions. This permits subsequent repair of bricks within individual furnace roof rings without fear that the remaining bricks forming such ring will fall into the furnace.

Now referring particularly to FIG. 2, it will be seen that roller or stamp embossing of a flat sheet produces a plurality of spacing portions or dimples 12, which project from and serve to space one surface .13 of the casing sheet from brick side face 2a, and a plurality of recesses 14, which are disposed in the other surface l of the casing sheet in alignment with spacing portions 12. Preferably embossment is effected by means of a plurality of generally cylindrical flat headed male die members which produce spacing portions and recesses of circular cross section wherein the side walls defining the spacing portions and recesses are disposed generally normal to sheet surfaces 13 and 15 and the trough and crest portions of the recesses and spacing portion, repectively, are flattened circular areas. Spacing portion 12 and recesses 14 are shown partciularly in FIGS. l, 3 and 4 as being arranged in a uniform pattern which is continuous of the casing sheet between the brick end faces 3a, 3b, which for purposes of clarity are shown in FIGS. l and 3 as being slightly spaced from the upper and lower marginal edges of the casing sheet. `It will be understood for purposes of reference that the flattened, circular crest portions of spacing portions 12 are disposed parallel to sheet surfaces 13 and |15 and cooperate to define a first engaging surface of the casing disposed in contact with the side faces of brick body 1.

It will now be seen by referring to FIGS. 3 and 4, that the at or non-embossed portions of sheet surfaces 13 and 15, which bound spacing portions 12 and recesses 14, are arranged generally in a latticework like pattern defined by intersecting first and second groups of parallel surface elements, indicated as 13', 13", and 15', 15", respectively. Again for purposes of reference, surface elements 15', 15", are considered to define a second engaging surface of casing 4 which is adapted to be disposed in contact with a like surface of a casing carried on an adjoining furnace roof brick.

Preferably, non-embossed sheet surface elements 13', 13", and 15', 15" are arranged so as to form an `acute angle of equal to or less than about 45 with a line 18', which is shown in FIG. 3 as extending lengthwise of brick body 1 between body and faces 3a, 3b. This arrangement of non-embossed sheet surface elements has been found to greatly increase the resistance of the casing to deforming forces encountered in a furnace roof construction which act generally along line 18 between the inner and outwardly facing surfaces of the roof. Further, by arranging spacing portions 12 and recesses 14 in a closely spaced uniform pattern and extending the pattern between the brick end faces, there is Obtained a uniform bearing stress distribution both between the casing and the side faces of the brick, and, as indicated in FIG. 6, between casing 4 and casing 4a carried on an adjacent brick body 1a. While in FIG. 6, the spacing portions and recesses on adjacently disposed casings 4 and 4a are shown to -be in alignment, accurate alignment thereof is not critical to insure alignment of forces existing within the joints along any given transverse longitudinal element of a roof construction. In this respect, it will be understood that the closely spaced groups of parallel surface elements 15', 15" present on the outwardly facing surfaces of each of the adjoining casings, as for instance 15 and 15a shown in FIG. 6, provide a plurality of closely spaced bearing points which insure uniform distribution of forces exerted within each roof joint and thus uniformally across any given element of the roof.

Further, the provision of at or non-embossed interconnected surface elements bounding recesses 14 acts to reduce the area of contact between adjacent brick casing surfaces and prevents interlocking of such surfaces due to discontinuities therein. This construction reduces frictional contact between adjacent bricks to a minimum and facilitates unobstructed sliding of the bricks into position during construction of a furnace roof.

Additionally, spacing portions and recesses when arranged in the pattern described, define tortuous paths between the end faces of the brick body which tend to prevent the passage of carborundous powder, known as Kish, which is normally present in the air surrounding a furnace, into the joints between adjacent bricks. Clearly, this is a particular desirable feature of the present invention, since if Kish were permitted to collect in the cavities created by the spacing portions, there would be no space to accommodate oxide layer growth or thermal expansion of the bricks.

A particularly important aspect of the present invention resides in the configuration and relative dimension of the individual portions 12 and recesses 14 with respect to the thickness of the non-embossed sheet from which the casing is to be formed. In this respect, it is well known that conventionally employed cold rolled low carbon steel casing sheet material will grow lto approximately twice its normal thickness when fully oxidized. Thus it has Ibeen found that growth in the overall thickness of a casing may be prevented by initially deforming an oxidizable metal sheet to provide a casing having aligned spacing portions and recesses having heights and depths, respectively, which are at least equal to the thickness of oxide layer growth on a non-embossed sheet of the type from which the casing is to be formed which is subject to complete oxidation. In effect, embossment of the oxidizable metal sheet produces a casing having at least double the thickness of the non-embossed sheet and the cavities defined by recesses 14 and the space between casing surface 13 and an adjoining side face of the brick are sufficient in size to accommodate the oxide layer formed on the casing.

The height of the crest portions of spacing portions 12 with respect to casing sheet surface 13 is increased over that necessary to accommodate oxide layer growth for the purpose of accommodating thermal expansion of the individual bricks. It will be apparent that when so modifying the heights of the spacing portions particular care must be taken in choosing the gage of the sheet metal employed in forming the casing and the dimensions and relative placement of the casing projections so as to insure controlled uniform collapse of the side walls of the spacing portions to accommodate brick growth due to thermal effects.

Casing design requirements Vary depending upon such factors as brick composition and dimension and operating conditions encountered in any given furnace roof construction. However, there has been found a family of casing designs having utility in the normal furnace roof construction which employs high re basic brick of the general composition disclosed above wherein the brick bodies may vary in widths between 2 inches and 6 inches and in lengths between 6 inches and 18 inches. The casings are formed from 22 to 26 gage, preferably from 25 to 26 gage, cold rolled low carbon steel sheet which is stamp embossed to provide spacing projections having -cross-sectional dimensions of between 1A and S wherein the distance between centers of adjacent projections vis no more than 1.5 inches, preferably no ymore than about 1.5 times said cross-sectional dimension of said projections. The preferred recessed depth has been established to be about 0.030 inch to about 0.045 inch, the recess depth may desirably and usually vary within a range between about 0.020 inch and 0.060 inch depending upon the degree of brick expansion due to thermal effects for which it is desired to compensate.

In special cases where it is desirable to compensate for growth of the refractory material due to thermal cycling, the embossment depth could be as high as 0.120 inch. For example, a 3 inch width brick may be fitted with a 26 gage sheet steel casing approximately 0.018 inch Ithick, the metal being embossed with 1/2 inch dia-meter circular pattern spaced on @A inch centers to a depth of 0.032 inch to accommodate oxidation of the plate and thermal expansion of the refractory. In roof ring construction it is common for the span of the arch to exceed 20 feet. The arch load imposed on the casing in each joint varies, but for large spans can result in a pressure of 50 p.s.i. Depending on metal thickness chosen for the casing the frequency and size of the embossment is selected so that the casing could support about 50 p.s.i. with less than 10% deformation in the projection height or recess depth.

A modified casing design is shown in FIG. 5, wherein a spacing portion and recess arrangement is provided on portions of the casing covering only brick side faces 2a, 2b which abut bricks within a given roof ring. This design may be readily employed in a roof construction wherein little bearing stress is present between bricks of adjacent roof rings, as for instance where all ring elements are of like dimension and curvature. In roof structures of this type only dimension changes within joints of each ring element are critical to proper roof design.

One difiiculty with employing casings of the type illustrated in FIG. 5 is that it is necessary to effect exact orientation of the embossed portions of the casing with respect to brick side faces 2a, 2b. An acceptable degree of orientation may however, be affected by a process wherein a blank of appropriate size is severed from a nonembossed coil of sheet material, subjected to stamp ernbossing, and thereafter folded about a brick and welded to form a unitary casing construction. When employing this process it is preferable to deform sheet marginal edge portion and form keying projection 6 simultaneously with the blanking operation to insure subsequent sheet orientation during embossment.

While not illustrated in the drawings, it will be apparent that the casing design shown in FIG. 5 may be further modified by omitting the embossment of that portion of the casing sheet which is adjacent brick side face 2b, while simultaneously providing an appropriate increase in the height of spacing projection 12 disposed in engagement with brick side face 2a. However the resultant thinning of the side walls of the spacing portions, and thus the reduction vin their ability to withstand a required bearing stress, may require a substantial increase of thickness of the sheet from which the casing is to be formed.

FIG. 6 illustrates a modification of the casing design shown in FIG. l, wherein the sole difference resides in the forming of the spacing portions 12 disposed adjacent the hot end face 3b of the brick body with tapered or inclined side walls in such a manner that the cross sectional area of the spacing projections progressively decreases, as the height of the spacing portions increase above casing surface 13. The desirability Of this modification is predicated upon the observed fact that during the effective life of a brick within a normal furnace roof construction approximately 60 to 75% of the hot end portion of the brick is consumed along with the adjacent portion of the casing following complete oxidation thereof. Also, it has been observed that the relatively cold end portion of the brick is often subjected to the highest bearing stress concentration and that the casing adjacent such cold end is oft times not exposed to complete oxidation even though the life time of the brick may include many months of furnace operation. It follows therefore that it is desired for any given casing material sheet thickness to form projections adjacent cold end of the brick body in such a manner that they Will withstand the highest stress concentration possible and to form the spacing projections adjacent the hot end of the brick body in such a manner that the oxidation growth of the casing proceeds in a controlled manner, prior to consumption thereof, so as to remove the possibility of their being created nonuniform oxide growth patterns within joints adjacent bricks.

The utilization of tapered or inclined side walls for the spacing portions and recesses have been found to facilitate a progressive and uniform collapse of such side walls upon oxide layer growth, which is not always possible if portions of such walls were to extend in a plane normal to sheet surfaces 13 and 15. This phenomena is explained by the fact that oxide layer growth is in a direction normal to the surface of the metal being oxidized, and thus by inclining the spacing portion and recess side walls with respect to a line disposed normal to the casing surfaces, a component of force set up due to growth of the oxide layer is always directed normal to the surface of the casing for the purpose of deforming the side walls. If, on the other hand, the side Walls are disposed normal to the surfaces of the casing sheet as would be the case wherein it is desired that the side walls possess maximum bearing strength, the oxide layer formed thereon would grow in a direction normal to the casing sheet surfaces and provide no component of force tending to force the spacing portion back into the plane of the casing sheet. Rather growth of an oxide layer in a direction parallel, for instance, to sheet surface 13 would interfere with the oxide layer formed on an adjacent non-embossed portion of such surface, such as surface elements 13', 13". This interference of oxide layers tends to result in uncontrollable high stress concentrations which may result in structural failure 0f the casing sheet prior to its being consumed or to serve to produce accumulations of oxide material which produce uncontrollable growth in overall sheet thickness non-uniformly across the surface thereof. Inclining of spacing portion side ,walls as the added advantage that such spacing portions tend to exhibit less of a tendency to collapse or fail due to forces set up within the roof structure which tend to shift or slide the bricks of one ring element with respect to the bricks on an adjacent ring element.

Thus, in the design illustrated in FIG. 6, relatively straight vertical side wall projection surfaces are utilized adjacent the cold end of the brick where maximum bearing stress is encountered in the absence of complete oxidation of the casing and tapered wall spacing portions are employed at least in that portion of the casing wherein there is complete casing oxidation so as to insure uniform oxide growth.

A further embodiment of the refractory brick according to the kpresent invention is illustrated in FIGS. 7 through 11, wherein elements common to the preferred embodiment illustrated in FIG. 1 are indicated by like numbers.

Now referring particularly to FIG. 7, it will be understood that this embodiment casing 4 is formed by severing a required length of embossed sheet material, wrapping the separate sheet completely around the brick body, and thereafter butt welding the meeting marginal edges thereof together, as at 20.

As in the case of the preferred embodiment, the casing sheet is formed by roller or stamp embossing a at sheet to produce a plurality of spacing portions or dimples 12a, which project from and serve to space one surface 13 of the casing sheet from brick side face 2a, and a plurality of recesses 14a which are disposed on the other surface 15 of the casing sheet in alignment with spacing portions 12a. Also, as clearly indicated in FIGS. 7, 9 and l0, the fiat or non-embossed portions of sheet surfaces 13 and 15, which bound spacing portions 12a and recesses 14a, are arranged generally in a latticework like pattern defined by intersecting first and second groups of parallel surface elements, indicated as 13', 13 and 15', 15" respectively. Preferably the non-embossed sheet surface elements 13', 13 and 15', 15" are arranged so as to form an acute angle a of equal to or less than about 45 with a line 18, which is shown in FIGS. 9 and 10 as extending lengthwise or brick body 1.

The structural design of spacing portions 12a and recesses 14a differ from those discussed with reference to the preferred embodiment in that they are of generally diamond shaped design wherein the side walls thereof are tapered or inclined with respect to the non-embossed surface portions of the casing sheet. Thus, as will be seen by reference to FIG. 8, the cross sectional area of the spacing portions progressively decreases, from sheet surface 13 toward the crest portions thereof.

While the crest portions of spacing portions 12a are shown in FIGS. 7 through l1 as being rounded, it will be understood that they may be flattened to provide a generally diamond shaped brick face engaging surface, if desired, to increase the degree of frictional contact between the casing and the side faces of the brick body. Also, embossments may be omitted from two or more faces of the brick body as discussed with reference to FIG. 5 and there may be a variation between the inclination of the sloping side walls of spacing portions 12 between the hot and cold ends of the brick body as discussed with reference to F'IG. 6.

FIG. l2 illustrates yet a further modification of the design and arrangement of the spacing portions of the casing structure illustrated in FIG. 1. In FIG. 12, the spacing portions are shown as being in the form of spaced sinusoidal ridges 12b, which extend either lengthwise or widthwise of the casing sheet carried upon any given brick body side face. As in the case of the second embodiment discussed, ridges 12b are formed by roll or stamp embossing a at sheet of oxidiza'ble metal casing material to form aligned spacing ridges and recesses, not shown, wherein the side walls thereof are inclined. Thus, the cross sectional area of the ridges progressively decreases, when viewed in FIG. l2, as the height of the ridges increase above the noninterconnected sheet surface 13b. In constructing a casing of this type, the amplitude of spacing ridges 12b does not appear to be critical, so long as the amplitude is correlated with the width thereof, as viewed in FIG. 12, so as to make the ridges individually discontinuous with respect to the length or width of the casing sheet along a straight line lying in the plane defined by such sheet; it being understood that this terminology is employed to distinguish the design illustrated in FIG. 12, as well as the other embodiment discussed, from prior casing structures provided with a plurality of parallel straight corrugations.

While reference has been made to employing the circular cross section spacing portions of the preferred embodiment of the present invention to space the casing from an adjacent side face of a brick body, it will be understood that such spacing portions may face outwardly with respect to the encased brick and engage like spacing portions of the casing on an adjacent brick, so long as the spacing portion of each casing are disposed in a closely spaced uniform pattern which prevents interlocking between adjacent casing engaging surfaces. However, except in an ideal situation wherein the spacing portions of adjacent casings are in alignment, the point by point contact between spacing portions does not permit the same uniformity of distribution of bearing stresses throughout the casings that is obtainable when the nonembossed surfaces of the casing are placed in engagement. Also, it will be understood that relatively outwardly projecting spacing portions may be provided on only one side surface of a wrap around casing and the crest portions thereof ernployed to engage a fiat or nonembossed side surface of a like wrap around casing carried on an adjoining brick of a furnace roof ring. This arrangement, while not suffering from the problem of interlocking between casings, does, however, require that the height of the spacing portions be substantially increased to accommodate oxidation expansion-of the adjacent nonembossed casing surface. This in turn would require that the thickness of the sheet from which the casing is formed be increased in order to compensate for the reduced wall thickness of the spacing portions, since wall thickness is directly proportional to the stress which the spacing portions will withstand before failure.

Also, while casing 4 has been described as being formed by roller or stamp embossing a single metal sheet which is thereafter wrapped completely around the brick body, it will understood that any conventional casing arrangement may be employed. Thus, casing sheets may be mounted individually on one, two, three or all four side faces of a brick body; a single casing sheet may be wrapped about only two or three adjacent brick body faces; or a casing may be formed from one or a pair of U-shaped casing sections adapted to cover three or four sides of the brick body, respectively. Additionally, conventional means other than the keying projections and recesses illustrated maybe employed to mount or position a casing sheet or sheets on the brick body.

Since these and Various modifications of the refractory brick disclosed will occur to others skilled in the art in view of the foregoing description, l wish to be limited only by the appended claims, wherein what is claimed is:

1. A refractory brick for use in furnace construction, said brick having side faces and first and second end portions, and-a casing of a single thickness of oxidizable metal sheet permanently secured on each of said side faces, said sheet characterized by a plurality of rows of projecting deformable spacing portions and a plurality of rows of projecting recess portions, said spacing portions having crest portions cooperating to define a first engaging surface, said recess portions having surrounding surface elements bounding said recess portions and defining a second engaging surface parallel to said first engaging surface, said first engaging surface being disposed in engagement with said brick side face and said second engaging surface being adapted to cooperate with the surrounding surface elements of a like casing secured on the face of an adjacent brick installed in a furnace construction, said surrounding surface elements and said recess portions being of dissimilar shape to prevent interlocking between adjacent bricks, said surrounding surface elements of one row being offset from surrounding surface elements of adjacent rows to resist deforming forces encountered in furnace construction and to prevent a direct flue affect between adjacent bricks, said sheet is fabricated from 22-26 gauge sheet metal, said recess portions have a depth of between 20-60 thousandths of an inch, said crest portions are of circular configuration with diameters of from 0.25 to 0.75 inch, the spacing between centers of adjacent crest portions is less than 1.5 times the diameter of said crest portions, the cross sectional areas of said spacing portions progressively decreases toward said crest portions engaging said brick first end portion adapted to be consumed during use in a furnace, one of said side faces of said brick having a slot recess extending lengthwise of said brick between said end faces, said sheet is wrapped about said side faces of said brick with marginal edges being overlapped and affixed together over said slot recess, said recess portions receiving oxidation formed on said sheet, said spacing portions being deformable under application of heat and pressure and upon oxidation thereof, whereby increase in overall sheet thickness is prevented.

2. The structure recited in claim 1, wherein said spacing portions adjacent said second brick end portion have sidewall portions surrounding said crest portions, said sidewall portions being normal to said brick second end portion.

References Cited UNITED STATES PATENTS l2 5/ 1937 Nyhagen, Jr. 11G-99X 3/1940 Griith 11G- 99X 8/ 1963 Frank et al. 52-232X 6/ 1964 Hall 52-232X 9/ 1965 Goodloe 52-403X 11/1966 Focht 52--598 7/ 1968 Dockerty 52-596 6/19615 Hall 110-99 FOREIGN PATENTS 7/ 1955 France 52-599 12/ 1962 France 52-598 12/1963 France 52-596 15 FRANK L. ABBOTT, Primary Examiner S. D. BURKE, Assistant Examiner U.S. C1. X.R. 

